Each year ~2.5 million people sustain a traumatic brain injury (TBI). Also a prominent general public health issue, TBI is particularly prevalent in Veterans, with 60-80% reporting a history of TBI. Over 80% of all TBI are categorized as mild TBI (mTBI), which is associated with a myriad of short- and long-term complications. Two of the principal complicating factors associated with mTBI are sleep-wake disturbances (e.g., insomnia, excessive daytime sleepiness, and circadian rhythm sleep disorders) and chronic pain, including headache and diffuse/global pain. Sleep-wake disturbances and chronic pain have an independent prevalence of ~70%, individually impair quality of life, impede effective rehabilitation, and have staggering economic impacts. Furthermore, there is a strong bidirectional relationship between sleep-wake disturbances and pain such that impaired sleep exacerbates pain, which leads to greater impairments in sleep and worse pain. This vicious cycle between sleep disturbances and pain, which is a particularly prevalent and detrimental condition in Veterans with chronic mTBI, represents a central challenge precluding effective treatment and ultimately, improving Veteran quality of life. Although there are pharmacological and non-pharmacological therapies for chronic pain, the presence of TBI significantly complicates the effectiveness of these treatment options, and have significant adverse effects (e.g., long-term prescription opioid dependence, misuse, and overdose). We believe there is profound potential to intervene at the sleep level, and, by improving sleep quality, enable Veterans with chronic mTBI to better manage their pain and end this vicious cycle. This proposal aims to apply a sleep intervention to improve chronic pain in Veterans with mTBI. We propose to use morning bright light therapy (MBLT), a readily deployable, cost-effective, non-pharmacologic, and home- based sleep intervention, to improve sleep-wake disturbances and therefore ameliorate chronic pain and improve quality of life in Veterans with chronic mTBI. There is substantial scientific precedent for MBLT to be effective in improving sleep quality, as outlined by a recent meta-analysis of 53 MBLT-based studies. Indeed, the potential of MBLT to improve sleep quality in Veterans with chronic mTBI remains unexplored, and yet, highly promising, especially in light of our exciting preliminary data supporting study feasibility and potential effectiveness. Our central hypothesis is that MBLT will improve sleep quality and ameliorate pain, resulting in improved quality of life in Veterans with chronic mTBI. Specific aims designed to test our hypothesis are to determine the effect of MBLT on, 1) sleep, 2) pain, and 3) quality of life, in Veterans with chronic mTBI. We propose to recruit n = 100 Veterans with mTBI from the VA Portland Health Care System, randomized 1:1 to MBLT (10,000 lux light exposure for 30 min within 90 min of waking for 4-weeks) or a no-light sham-MBLT condition (as previously published using the same duration/timing). Sleep quality will be assessed through self-report questionnaires and 24/7 actigraphy monitoring. Pain will be evaluated through self-report questionnaires and two quantitative methods (conditioned pain modulation and pressure algometry). Quality of life will be measured through self-report questionnaires. Outcomes will be assessed pre- and post-intervention, and at a 3-month follow-up time point. It is expected the proposed work will demonstrate MBLT is a viable method for improving sleep quality, ameliorating chronic pain and improving quality of life, in Veterans with mTBI. Improvements in pain and quality of life will positively correlate with objective markers of improved sleep quality. These data would demonstrate, 1) an effective treatment option, alone or in combination with existing rehabilitative efforts, in Veterans with mTBI, and 2) sleep-wake disturbances may be implicated in the pathogenesis of these functional impairments, thereby establishing greater precedent for targeting sleep as a meaningful primary and/or adjunctive rehabilitative therapy.